In the descriptions of the present invention, a cultivator will be described as a representative example of a plow which is most mainly used among a variety of cultivators, but it is not limited thereto.
In general, the plow has been used for the sake of cultivation of various plants, wherein soil is excavated and turned over using domestic animals, for example, horses and cow, a machine, etc., thus making ridges.
A conventional plow apparatus detachably attached to a tractor is equipped with a multiple plow device formed of a plurality of plowing units which are selected based on the size and horse power of the tractor. The conventional plow apparatus for a tractor is equipped with three or eight plowing units. Each plowing unit may be installed in a zigzag direction with respect to a main frame or may be installed at a main frame in a diagonal line with respect to a towing direction.
When a plowing work is carried out using a conventional plow apparatus for a tractor, a plowing unit may collide with a rock hidden in soil. If the plowing unit is fixedly installed at the main frame, the plowing unit may directly receive the impulsive force from the rock, for which the plowing unit may be broken or deformed, so the shape of a furrow may collapse or the apparatus may have a problem.
The Korean patent registration No. 10-1117769 filed by the same applicant as the present invention describes a safety apparatus which is able to prevent any damage to a plowing unit.
The aforementioned conventional device for a tractor includes a main frame equipped with a tractor connection unit the front of which is connected to a tractor for the sake of towing, a plurality of plowing units installed rotatable at the main frame, a plurality of driving cylinders which are able to rotate upward and downward each of the plowing units, a cushioning cylinder which is fixedly installed at the main frame and is engaged slidable for a piston rod to come in and out, a first hydraulic line which is employed to connect one side of the driving cylinder and the cushioning cylinder, an assistant cylinder which is fixedly installed at the main frame and is engages slidable for the piston rod to come in and out, a second hydraulic line which is employed to connect the other side of the cushioning cylinder and one side of the assistant cylinder, and a third hydraulic line which is employed to connect the other side of the assistant cylinder and the other side of the driving cylinder.
The operation thereof will be described. If the plowing unit contacts with a rock, it will rotate upward by means of an external force due to the rock, and the hydraulic pressure inside of the driving cylinder will move via the first hydraulic line to an inlet port of the cushioning cylinder, and the cylinder rod will slide into the inside of the cushioning cylinder, and the hydraulic pressure inside of the cushioning cylinder may discharge via an outlet port, an inlet port of the assistant cylinder and the second hydraulic line.
The cylinder rod of the assistant cylinder will slide into the inside of the assistant cylinder, and the hydraulic pressure of the inside thereof will discharge via the outlet port and will move toward the other side of the driving cylinder via the third hydraulic line, thus absorbing an over pressure which has been generated due to the rock.
If the plowing unit, which has rotated upward due to the rock, returns back to its initial position, the hydraulic pressure will, on the contrary, move into the assistant cylinder and the cushioning cylinder. More specifically, the hydraulic pressure which has moved in from the other side of the driving cylinder, will be inputted into the outlet port of the assistant cylinder via the third hydraulic line, by which the cylinder rod is pushed and exposed to the outside, and the hydraulic pressure inside of the assistant cylinder will discharge via the inlet port and will be inputted into the outlet port of the cushioning cylinder via the second hydraulic line.
As the cylinder rod of the cushioning cylinder is exposed to the outside, the inside hydraulic pressure may be inputted into the driving cylinder via the first hydraulic line, so it can return back to its initial position.
A spring is installed inside of the assistant cylinder so as to elastically support the cylinder rod of the assistant cylinder, by means of which the cylinder rod can be elastically supported when it is inserted inside by means of the inputted hydraulic pressure.
In the conventional technology, there, however, should be provided a plurality of the hydraulic lines to connect the driving cylinder, the assistant cylinder, and the cushioning cylinder, for which the configuration may become very complicated, and the manufacturing may cost a lot.
Since the assistant cylinder is equipped with a spring which is disposed inside of the same, the hydraulic pressure which has discharged from the assistant cylinder when the plow excavates soil, may be inputted via the third hydraulic cylinder into the driving cylinder. For this reason, the cylinder rod may be retracted, by means of which the plow may be tilted backward little by little even though a predetermined obstacle, for example, a rock, etc. is not met. So, the soil may not be cultivated evenly.